1. Field of the Invention
The present invention relates to a metal alkoxide compound having a novel specific structure, a material for forming a thin film containing the compound, and a method for producing a thin film using the material.
2. Description of the Related Art
A thin film that contains titanium, zirconium or hafnium is used as an electronic member for electronic components such as high-dielectric capacitors, ferroelectric capacitors, gate insulating films and barrier films, or an optical member for optical communication devices such as optical wave guides, optical switches, and optical amplifiers.
As a method for producing the above thin film, there may be mentioned flame deposition, sputtering, ion plating, MOD such as coating thermal decomposition and sol-gel processes, chemical vapor deposition, or the like. Among these, chemical vapor deposition (hereinafter, may be simply referred to as “CVD”) including Atomic Layer Deposition (ALD) is an appropriate production process, because of its many advantages including excellent properties in composition control and step coverage, suitability for mass production, capability of providing hybrid integration, and the like.
In the CVD process, a metal compound having organic ligands is used as a precursor supplying metal atoms source for a thin film. A compound (precursor) suitable for materials used in CVD is required to have such properties as being transportable in a liquid state upon vaporization and at transportation, having a high vapor pressure and being easy to evaporate, and being stable against heat. In addition, upon thin film deposition, the decomposition is easily progressed by thermal and/or chemical reaction. As the precursors of titanium, zirconium and hafnium, tetrakis-dialkylamide compounds and tetrakis-alkoxide compounds have been examined.
Patent Documents 1 to 4 disclose tetrakis-amide compounds. Patent Documents 5 to 7 disclose tetrakis-alkoxide compounds. Patent Document 8 discloses tetrakis-amide compounds, tetrakis-alkoxide compounds and the like. Further, in claim 1 of Patent Document 9, a metal alkoxide compound represented by M(OR′)4 (R′ is an alkyl group or alkenyl group that has 2 to 21 carbon atoms and may be branched; and M is zirconium, hafnium or titanium) is disclosed. However, regarding the alkenyl group, no specific structure is disclosed.
Patent Document 1: Japanese Patent Laid-Open Publication No. 2002-93803
Patent Document 2: Japanese Patent Laid-Open Publication No. 2002-93804
Patent Document 3: Korean Patent No. 156980
Patent Document 4: Japanese Patent Laid-Open Publication No. 2006-182709
Patent Document 5: Japanese Patent Laid-Open Publication No. H5-239650
Patent Document 6: Japanese Patent Application Publication No. H6-60406
Patent Document 7: Japanese Patent Laid-Open Publication No. 2002-69641
Patent Document 8: Japanese Patent Laid-Open Publication No. 2005-340405
Patent Document 9: Japanese Patent Laid-Open Publication No. S60-258132
Tetrakis-dialkylamide compounds have problems in thermal stability, and have a disadvantage in stable production of thin films. Further, tetrakis-alkoxide compounds are not sufficiently decomposed on thin film deposition, and have problems in productivity.